Microalgae Chlorella vulgaris Immobilized in Calcium Alginate Versus Free Cells: Growth in Mixotrophic and Autotrophic Conditions for Characterization of Fatty Acids by GC-MS

Abstract

This study evaluated the mixotrophic cultivation of Chlorella vulgaris using free and sodium alginate-immobilized cells in a medium composed of Bold’s Basal Medium (BBM) and an industrial effluent (MEM) at a 1:1 ratio. Cultures were maintained at pH 6.8, 30 ± 2 °C, under a 16:8 h light/dark photoperiod, and monitored for eight days through cell counts and absorbance measurements. Early contamination by cyanobacteria compromised the growth of C. vulgaris in free cultures; however, a 1 µm membrane ultrafiltration protocol successfully purified the microalgal cultures. Cell immobilization did not enhance biomass production. The results demonstrated the potential of industrial effluents as alternative media for C. vulgaris cultivation, with prospects for biodiesel production containing lower linolenic acid levels. Immobilized pure cultures exhibited lighter coloration, likely due to environmental constraints within the alginate matrix. Although the alginate/algae concentration initially showed satisfactory performance, further optimization is required to prevent the escape and growth of free cells outside the microcapsules. Overall, the findings highlight the importance of optimizing cultivation conditions and alginate concentrations to maximize biomass yield and increase palmitic acid production for esterification processes.